NOAA/WDS Paleoclimatology - Southern Continental Margin of Australia Benthic Foraminifera Stable Isotope Data, Lynch-Stieglitz 1994

STUDY NOTES: Sample preparation notes- Common acid bath, MAT 251, roasted before analysis, measurements on grouped foraminifera Data comes from these South Indian Ocean cores: Core Name Lat Lon Depth RS67-GC3 -37.55 138.583 1476 m RS67-GC13 -38.465 140.167 2525 m RS67-GC16 -38.333 140.182 1650 m RS67-GC27 -38.648 141.192 506 m RS67-GC52 -41.182 143.958 1145 m RS78-GC18 -41.385 144.233 814 m SO36-SL7 -42.31 144.67 1085 m SO36-SL17 -42.05 144.59 1042 m VM18-222 -38.567 140.617 1904 m Provided Keywords: Australia, benthic foraminifera, isotopes, Last Glacial Maximum
ABSTRACT SUPPLIED BY ORIGINATOR: Sediment cores from the southern continental margin of Australia are near the formation region of Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water and record the changes in these water masses from the last glacial maximum through the present. Carbon and oxygen isotopes were measured on the benthic foraminiferal species Planulina wuellerstrorfi for both the Recent and last glacial maximum sections of the cores and were then used to reconstruct temperature and carbon isotopic water column profiles. The glacial oxygen isotope profile indicates a vertical temperature structure for this region similar to that in today's Subantarctic Zone. Although intermediate water d13C cannot be used as a nutrient tracer in this region because of the large influence of air-sea carbon isotopic exchange on this water mass, d13C can be used as a water mass tracer. Today, AAIW properties reflect contributions from cool, fresh Antarctic Surface Waters (2/3) and warm, salty waters from the Indian Ocean (1/3). When examined in conjuction with the glacial d13C and d18C data from the north Indian and Southern Oceans, our data suggest a much reduced contribution of North Indian Ocean intermediate water to glacial Antarctic Intermediate Water relative to the contribution of Antarctic Surface Water. This fresher, cooler glacial Antarctic Intermediate Water would be distributed to the intermediate-depth ocean, thus decreasing the transport of salt produced in the North Indian Ocean to the rest of the world's oceans. Combined with evidence for a reduced influence of North Atlantic Deep Water, these results suggest major changes in the pathways for the redistribution of heat and salt in the glacial ocean.